The Conservative Party will never scoop up all the votes of the 52 per cent who voted Leave. It needs a sizeable chunk of the 48 per cent who backed Remain to form a Government with a sustainable majority. It hasn’t had one for the best part of 30 years.

That 48 per cent is a very mixed bag. Much of it is now reconciled to Brexit. But there is a substantial chunk of it still opposed to the project, concentrated in the parts of the country that voted Remain: largely London, parts of the greater South-East, bits of other big cities, the University towns, Scotland. Another, doubtless larger slice of it – aligned to bigger business and other interests – wants a Soft Brexit. So do some Leave voters.

This is not in our view the majority take in the country, but it is an important element in it – and not one that the Conservative Party can ignore. As Margaret Thatcher once put it about the Party’s left and right, a bird needs two wings to fly. Her insight applies as much to Brexit today as to economics then. History suggests that the Tories have no winning future shorn of one part of their centre-right coalition. There are unlikely to be enough purple votes in the right places to compensate for the loss of turquoise ones.

The leaving of the Conservative whip, and the decision to “sit alongside” the Independent Group by three Tory MPs today, should be seen against that perspective. Two of them were fairly recent arrivals in the Party – Heidi Allen and Sarah Wollaston. Neither ever acclimatised to the partisan culture of Westminster. Both have had trouble with their local Associations. Neither have been promoted up the food chain of office. Both leave the Government even more shorn of a sustainable majority, and just a bit nearer another general election.

So does Anna Soubry. Otherwise, she is a horse of a different colour – nature, anyway. A former very senior Minister, Soubry has a very longstanding Party attachment, of which this site has vivid memories. Constistently (and wrongly in our view) she has, over the course of over 30 years, unblinkingly held the Conservative Right responsible for every problem that the Party has endured, and as far as we can see the country too. She insists that she didn’t join the SDP during the 1980s. Now she has the chance to make up for it.

Living in a family part of which one detests can only be bad for the soul, and in that narrow sense Soubry has made the right decision – as have her colleagues. We are sad that it’s happened, but also believe, with a heavy heart, that it’s necessary. On Brexit, the three were in flagrant breach of the manifesto on which they stood and assurances they had previously given. All voted to move Article 50. All supported the EU Withdrawal Bill. Their position had become impossible. It is best for them to leave.

Spare a thought this morning for the local activists who gave money, made phone calls, knocked on doors, supported events – and backed this gang of three. Many of them will feel desolated if not betrayed. It is worth noting that a fear of deselection will not have been the motive in all of these cases. As far as we know, Soubry was well placed in Broxtowe: indeed, she saw off an attempt by her former Chairman to get rid of her last year.

At any rate, all are gone. The wording of their statement about the new Independent Group is odd – suggesting a touch of doubt, hesitation and confusion. They must be in for a pound (or a euro) if they’re in for a penny – especially since, presumably, there is no going back. In their statement earlier this week, the Labour seven made only passing reference to Brexit. But it is at the heart of the statement from the Gang of Three. That’s a sign that the new grouping will be no more immune from division than the main parties.

How big a moment is this? Perhaps numbers offer the answer. Christopher Brocklebank-Fowler was the only Tory MP to cross the floor and join the SDP. Then there was one; now there are three. More may follow. Downing Street will feel a mix of relief and fear at what’s happened – and ponder the loss of three of the Party’s women MPs. If Wollaston, Soubry and Allen join the new party that will emerge from the Independent Group, they should face by-elections. In the meantime, “nothing extenuate, nor set down aught in malice”.

Though if you insist on a last laugh, mull this thought. They may all have jumped at exactly the wrong moment – just as Theresa May, whose obtaining of a deal they had despaired of, could be on the verge of pulling one off.